Title: An investigation of the microstructure and ductility of annealed cold-rolled tungsten

Abstract

Tungsten is notoriously brittle metal at room temperature. Furthermore, contrary to most metals, plastic deformation increases ductility and recrystallization decreases ductility of tungsten. The fundamentals that govern this behavior have challenged academia and industry for decades. This paper focuses on understanding the controlling factors of ductility through a systematic investigation of the changes in microstructure and mechanical properties of cold-rolled tungsten that occur during annealing. Cold-rolled tungsten samples were annealed at temperatures up to 1400 °C, and mechanical testing and microstructural analysis was performed before and after annealing. Furthermore, a dislocation mobility model based on the Orowan equation was applied. The mechanisms of deformation are discussed within the context of deformed and annealed microstructures. The high fraction of low angle grain boundaries and high density of edge dislocations were found to be the most important factors for ductility. Although there were gradual changes in microstructure and mechanical properties, the ductility of cold-rolled tungsten was maintained up to 1300 °C. The material recrystallized when annealed above this temperature, had no ductility, and suffered brittle fracture. Microstructural characterizations of the as-rolled material revealed a typical BCC texture, with grains elongated in rolling direction and a large amount of edge dislocations and lowmore » angle grain boundaries. The level of texturing and the fraction of low angle grain boundaries diminished after recrystallization. It was found that, compared to the recrystallized material, as-rolled tungsten can accommodate over 7 orders of magnitude higher deformation velocity due to the high density of edge dislocations.« less

Authors:

Ren, Chai  ^[1];

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Fang, Z. Zak ^[1]; Xu, Lei ^[1]; Ligda, Jonathan P. ^[2]; Paramore, James D. ^[3]; Butler, Brady G. ^[2]

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+ Show Author Affiliations

1. Univ. of Utah, Salt Lake City, UT (United States)
2. Army Research Lab., Aberdeen, MD (United States)
3. Univ. of Utah, Salt Lake City, UT (United States); Army Research Lab., Aberdeen, MD (United States)

Publication Date:

Wed Oct 10 00:00:00 EDT 2018

Research Org.:

Univ. of Utah, Salt Lake City, UT (United States); Heavystone Lab., LLC, Park City, UT (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1611116

Alternate Identifier(s):

OSTI ID: 1636963

Grant/Contract Number:  

SC0008673; SC0017772; DESC0008673; DESC0017772; W15QKN-13-C-0068; W15QKN-15-C-0038; DMR-1121252

Resource Type:

Accepted Manuscript

Journal Name:

Acta Materialia

Additional Journal Information:

Journal Volume: 162; Journal Issue: C; Journal ID: ISSN 1359-6454

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; Materials Science; Metallurgy & Metallurgical Engineering; Tungsten; Ductility; Microstructure; Mechanical properties; Annealing